Installation

Before you begin

This tutorial assumes that you have already followed the steps in Installing Pyramid, except do not create a virtual environment or install Pyramid. Thereby you will satisfy the following requirements.

Install SQLite3 and its development packages

If you used a package manager to install your Python or if you compiled your Python from source, then you must install SQLite3 and its development packages. If you downloaded your Python as an installer from https://www.python.org, then you already have it installed and can skip this step.

If you need to install the SQLite3 packages, then, for example, using the Debian system and apt-get, the command would be the following:

sudo apt-get install libsqlite3-dev

Install cookiecutter

We will use a cookiecutter to create a Python package project from a Python package project template. See Cookiecutter Installation for instructions.

Generate a Pyramid project from a cookiecutter

We will create a Pyramid project in your home directory for Unix or at the root for Windows. It is assumed you know the path to where you installed cookiecutter. Issue the following commands and override the defaults in the prompts as follows.

On Unix

cd ~
cookiecutter gh:Pylons/pyramid-cookiecutter-starter --checkout 2.0-branch

On Windows

cd \
cookiecutter gh:Pylons/pyramid-cookiecutter-starter --checkout 2.0-branch

On all operating systems

If prompted for the first item, accept the default yes by hitting return.

You've cloned ~/.cookiecutters/pyramid-cookiecutter-starter before.
Is it okay to delete and re-clone it? [yes]: yes
project_name [Pyramid Scaffold]: myproj
repo_name [myproj]: tutorial
Select template_language:
1 - jinja2
2 - chameleon
3 - mako
Choose from 1, 2, 3 [1]: 1
Select backend:
1 - none
2 - sqlalchemy
3 - zodb
Choose from 1, 2, 3 [1]: 2

Change directory into your newly created project

On Unix

cd tutorial

On Windows

cd tutorial

Set and use a VENV environment variable

We will set the VENV environment variable to the absolute path of the virtual environment, and use it going forward.

On Unix

export VENV=~/tutorial

On Windows

set VENV=c:\tutorial

Create a virtual environment

On Unix

python3 -m venv $VENV

On Windows

python -m venv %VENV%

Upgrade packaging tools in the virtual environment

On Unix

$VENV/bin/pip install --upgrade pip setuptools

On Windows

%VENV%\Scripts\pip install --upgrade pip setuptools

Installing the project in development mode

In order to do development on the project easily, you must "register" the project as a development egg in your workspace. We will install testing requirements at the same time. We do so with the following command.

On Unix

$VENV/bin/pip install -e ".[testing]"

On Windows

%VENV%\Scripts\pip install -e ".[testing]"

On all operating systems

The console will show pip checking for packages and installing missing packages. Success executing this command will show a line like the following:

Successfully installed Jinja2-2.11.2 Mako-1.1.3 MarkupSafe-1.1.1 PasteDeploy-2.1.1 Pygments-2.7.3 SQLAlchemy-1.3.22 WebTest-2.0.35 alembic-1.4.3 attrs-20.3.0 beautifulsoup4-4.9.3 coverage-5.3.1 hupper-1.10.2 iniconfig-1.1.1 packaging-20.8 plaster-1.0 plaster-pastedeploy-0.7 pluggy-0.13.1 py-1.10.0 pyparsing-2.4.7 pyramid-1.10.5 pyramid-debugtoolbar-4.9 pyramid-jinja2-2.8 pyramid-mako-1.1.0 pyramid-retry-2.1.1 pyramid-tm-2.4 pytest-6.2.1 pytest-cov-2.10.1 python-dateutil-2.8.1 python-editor-1.0.4 repoze.lru-0.7 six-1.15.0 soupsieve-2.1 toml-0.10.2 transaction-3.0.1 translationstring-1.4 tutorial venusian-3.0.0 waitress-1.4.4 webob-1.8.6 zope.deprecation-4.4.0 zope.interface-5.2.0 zope.sqlalchemy-1.3

Testing requirements are defined in our project's setup.py file, in the tests_require and extras_require stanzas.

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tests_require = [
    'WebTest',
    'pytest',
    'pytest-cov',
]
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    extras_require={
        'testing': tests_require,
    },

Initialize and upgrade the database using Alembic

We use Alembic to manage our database initialization and migrations.

Generate your first revision.

On Unix

$VENV/bin/alembic -c development.ini revision --autogenerate -m "init"

On Windows

%VENV%\Scripts\alembic -c development.ini revision --autogenerate -m "init"

The output to your console should be something like this:

2021-01-07 05:15:57,709 INFO  [alembic.runtime.migration:155][MainThread] Context impl SQLiteImpl.
2021-01-07 05:15:57,709 INFO  [alembic.runtime.migration:162][MainThread] Will assume non-transactional DDL.
2021-01-07 05:15:57,712 INFO  [alembic.autogenerate.compare:134][MainThread] Detected added table 'models'
2021-01-07 05:15:57,712 INFO  [alembic.autogenerate.compare:588][MainThread] Detected added index 'my_index' on '['name']'
  Generating <somepath>/tutorial/tutorial/alembic/versions/20210107_d7ab09c3fdec.py ...  done

Upgrade to that revision.

On Unix

$VENV/bin/alembic -c development.ini upgrade head

On Windows

%VENV%\Scripts\alembic -c development.ini upgrade head

The output to your console should be something like this:

2021-01-07 05:16:21,558 INFO  [alembic.runtime.migration:155][MainThread] Context impl SQLiteImpl.
2021-01-07 05:16:21,558 INFO  [alembic.runtime.migration:162][MainThread] Will assume non-transactional DDL.
2021-01-07 05:16:21,560 INFO  [alembic.runtime.migration:517][MainThread] Running upgrade  -> d7ab09c3fdec, init

Load default data

Load default data into the database using a console script. Type the following command, making sure you are still in the tutorial directory (the directory with a development.ini in it):

On Unix

$VENV/bin/initialize_tutorial_db development.ini

On Windows

%VENV%\Scripts\initialize_tutorial_db development.ini

There should be no output to your console. You should now have a tutorial.sqlite file in your current working directory. This is an SQLite database with three tables defined in it, alembic_version, models, and master, where the first two tables each have single record inside of them.

Run the tests

After you've installed the project in development mode as well as the testing requirements, you may run the tests for the project. The following commands provide options to pytest that specify the module for which its tests shall be run, and to run pytest in quiet mode.

On Unix

$VENV/bin/pytest -q

On Windows

%VENV%\Scripts\pytest -q

For a successful test run, you should see output that ends like this:

.....
5 passed in 0.44 seconds

Expose test coverage information

You can run the pytest command to see test coverage information. This runs the tests in the same way that pytest does, but provides additional coverage information, exposing which lines of your project are covered by the tests.

We've already installed the pytest-cov package into our virtual environment, so we can run the tests with coverage.

On Unix

$VENV/bin/pytest --cov --cov-report=term-missing

On Windows

%VENV%\Scripts\pytest --cov --cov-report=term-missing

If successful, you will see output something like this:

======================== test session starts ========================
platform darwin -- Python 3.9.0, pytest-6.2.1, py-1.10.0, pluggy-0.13.1
rootdir: <somepath>/tutorial, inifile: pytest.ini, testpaths: tutorial, tests
plugins: cov-2.10.1
collected 5 items

tests/test_functional.py ..                                                           [ 40%]
tests/test_views.py ...                                                               [100%]

---------- coverage: platform darwin, python 3.9.0-final-0 -----------
Name                                                 Stmts   Miss  Cover   Missing
----------------------------------------------------------------------------------
tutorial/__init__.py                                     8      0   100%
tutorial/alembic/env.py                                 23      4    83%   28-30, 56
tutorial/alembic/versions/20200106_8c274fe5f3c4.py      12      2    83%   31-32
tutorial/models/__init__.py                             32      2    94%   71, 82
tutorial/models/meta.py                                  5      0   100%
tutorial/models/mymodel.py                               8      0   100%
tutorial/pshell.py                                       7      5    29%   5-13
tutorial/routes.py                                       3      0   100%
tutorial/scripts/__init__.py                             0      0   100%
tutorial/scripts/initialize_db.py                       22     14    36%   15-16, 20-25, 29-38
tutorial/views/__init__.py                               0      0   100%
tutorial/views/default.py                               13      0   100%
tutorial/views/notfound.py                               5      0   100%
----------------------------------------------------------------------------------
TOTAL                                                  138     27    80%

===================== 5 passed in 0.77 seconds ======================

Our package doesn't quite have 100% test coverage.

Test and coverage cookiecutter defaults

The Pyramid cookiecutter includes configuration defaults for pytest and test coverage. These configuration files are pytest.ini and .coveragerc, located at the root of your package.

pytest follows conventions for Python test discovery. The configuration defaults from the cookiecutter tell pytest where to find the module on which we want to run tests and coverage.

See also

See pytest's documentation for Usage and Invocations or invoke pytest -h to see its full set of options.

Start the application

Start the application. See What Is This pserve Thing for more information on pserve.

On Unix

$VENV/bin/pserve development.ini --reload

On Windows

%VENV%\Scripts\pserve development.ini --reload

Note

Your OS firewall, if any, may pop up a dialog asking for authorization to allow python to accept incoming network connections.

If successful, you will see something like this on your console:

Starting monitor for PID 68932.
Starting server in PID 68932.
Serving on http://localhost:6543
Serving on http://localhost:6543

This means the server is ready to accept requests.

Visit the application in a browser

In a browser, visit http://localhost:6543/. You will see the generated application's default page.

One thing you'll notice is the "debug toolbar" icon on right hand side of the page. You can read more about the purpose of the icon at The Debug Toolbar. It allows you to get information about your application while you develop.

Decisions the cookiecutter backend option sqlalchemy has made for you

When creating a project and selecting the backend option of sqlalchemy, the cookiecutter makes the following assumptions:

  • You are willing to use SQLite for persistent storage, although almost any SQL database could be used with SQLAlchemy.

  • You are willing to use SQLAlchemy for a database access tool.

  • You are willing to use Alembic for a database migrations tool.

  • You are willing to use a console script for a data loading tool.

  • You are willing to use URL dispatch to map URLs to code.

  • You want to use zope.sqlalchemy, pyramid_tm, and the transaction packages to scope sessions to requests.

Note

Pyramid supports any persistent storage mechanism (e.g., object database or filesystem files). It also supports an additional mechanism to map URLs to code (traversal). However, for the purposes of this tutorial, we'll only be using URL dispatch and SQLAlchemy.